Anti-theft devices which prevent auto theft are conventionally known. A thief may attempt to steal a vehicle or valuables in the vehicle that has been installed with such an anti-theft device by opening a door of the vehicle, opening a trunk, or by breaking a window. Sensors such as motion detectors, vibration detectors, sound detectors, shock sensors, pressure sensors and mechanical switches are used to detect such an intrusion. Upon detection of the intrusion, the anti-theft device actuates a siren and flashes the vehicle headlamps to ward off the thief.
However, the sensors in the anti-theft devices are prone to false actuations. For example, a shock sensor may be actuated by force applied from the outside or a sound sensor may be actuated by excessive external noise without any thief being present. False alarms inconvenience the owner who has to return to the vehicle to turn off the alarm as well as the neighbors who must endure the siren noise until the owner turns off the alarm. On the other hand, when the vehicle is actually being stolen, it may be sometimes dangerous for the owner to approach the vehicle alone. In both cases, the owner will want to ascertain the status of the vehicle before approaching the vehicle.
U.S. Pat. No. 5,335,264 to Namekawa discloses a vehicle security system including a vehicle mounted unit, a vehicle mounted cellular telephone unit and a hand-held remote unit, which is incorporated herein by reference. When the vehicle unit detects an abnormal condition, it sends an alarm signal to the remote unit and turns on the cellular telephone within the vehicle so that it is ready to receive a call, presumably the owner who has received the alarm signal through the remote unit. When the telephone call is received and an “inside sound receiving code” is also received, the vehicle unit connects the cellular telephone's microphone to the transmitter so that the sound within the vehicle can be monitored through the owner's cellular telephone.
However, a problem with the Namekawa system is that it relies on a public cellular telephone network. That means that the system will not operate if either the cellular telephone in the vehicle or the owner's cellular telephone is outside of the telephone service area. Another problem with the Namekawa system is that once intrusion has been detected, no action may be taken if the owner's remote control unit does not receive the indication of intrusion detection. For example, the remote control unit may have been intentionally turned off by the owner or the battery may have died. In that case, there is nothing to prevent the intruder from stealing the vehicle or any component of the vehicle. Moreover, even if the owner verifies an actual intrusion through the sound monitoring, the Namekawa system does not provide any way to prevent the theft.
Therefore, it is desirable to provide improved anti-theft system that does not rely on connection to a telephone network. It is also desirable to provide the system with an ability to prevent the theft once intrusion has been verified.